France’s longest viaduct sits half-finished over the Indian Ocean, and the people of Reunion Island are still paying the price. The 5.4-kilometer structure that opened in 2022 represents only the first half of an infrastructure project designed to eliminate reliance on a cliff road that has claimed 22 lives since 1976. Completion remains years away, leaving commuters and residents caught between an unfinished modern highway and the aging, hazardous coastal route it was meant to replace.
The original coastal road, opened in 1976, continues to pose serious dangers to everyday travelers. Rock falls, powerful swells, and frequent closures have made this stretch a persistent public safety concern. Twenty-two deaths recorded on this road underscore that the stakes extend far beyond engineering timelines. For residents and commuters in the region, the incomplete project means continued exposure to conditions that authorities themselves deemed unsafe enough to warrant a major infrastructure overhaul.
The first viaduct section, completed in 2019 and operational since 2022, stretches 5,409 meters across 48 supporting pillars, connecting Saint-Denis to Grande Chaloupe. Its construction consumed approximately 300,000 cubic meters of concrete and 38,000 tonnes of steel, all deployed in an environment where saltwater corrosion and cyclonic swells create constant structural challenges. The structure was engineered to lift traffic away from the unstable cliff face that characterizes this section of Reunion’s coastline. Yet upon reaching Grande Chaloupe, drivers must still descend back onto the original coastal road to continue their journey, creating an illogical patchwork of modern and aging infrastructure.
The original plan envisioned a massive sea dike extending from the first viaduct to La Possession, a solution that seemed more straightforward than building a second bridge over open ocean. That approach required millions of tonnes of rock material. The proposed Bois-Blanc quarry in Saint-Leu became a focal point of community resistance, with residents, local associations, and elected officials raising concerns about noise, dust, and truck traffic. Legal challenges blocked the quarry project, leaving planners without the raw materials necessary to proceed with the dike option.
Faced with this impasse, the Reunion Region government reversed course entirely.
The solution initially deemed too expensive and ambitious has become the only viable path forward: a second maritime viaduct spanning approximately 2.5 kilometers from Grande Chaloupe to La Possession. In 2025, regional authorities validated an 846-million-euro authorization for the work, with the 2026 budget confirming continued funding. The target completion date stands at 2030.
The remaining construction will unfold in phases. Preparatory work at La Possession comes first, including maritime protections and reconfiguration of the interchange system. A new road connector will gradually redirect traffic toward the future structure. The second viaduct will then be built across a zone particularly vulnerable to cyclonic swells and salt corrosion, requiring precise engineering for each supporting pillar.
This second viaduct must be engineered from the outset for an aggressive marine environment. The initial design assumptions, the hostile sea conditions, and community opposition to resource extraction have fundamentally reshaped both the timeline and the approach.
For the public using this route daily, the question is whether completion by 2030 will finally deliver the safe, continuous passage that was promised years ago, and whether the engineering solutions chosen for the second viaduct will prove equal to the same ocean that has made this coastline so dangerous for so long.